Endoscopes and imaging catheters are widely used in many medical procedures for viewing areas of bodily organs, cavities, passageways, etc. Generally, such imaging devices include an elongated sheath or similar structure wherein optical fibers are arranged both for transmitting illumination light to the distal end of the sheath to illuminate a viewing field, and for carrying an optical image back to a viewing port or camera. One or more lenses may be positioned on the distal end of the imaging device to focus the optical image received by, or the illumination cast by the instrument.
In many applications, it is desirable that the distal portion of the imaging device be “steerable”, bendable or maneuverable from the proximal end of the device to facilitate guidance of the device through tortuous or furcated anatomical passageways. Additionally, the ability to bend the device at or near its distal end may enable the operator to visually scan an expanded viewing area by bending or otherwise manipulating the distal end of the device. The ability to maneuver the tip makes it easier to guide the tip of the device properly through the often highly branched and convoluted passageways near organs.
In order to effect and control the deflection of the distal tip of an imaging device, many designs have been introduced that incorporate either two opposed control wires to control bending in one plane, or four wires evenly spaced to control bending in two perpendicular planes. These control wires run the length of the device and terminate at the distal end of the steerable region or at the distal tip. The proximal end of each control wire is functionally connected to a separate drum or spool rotated manually or by a dedicated electrical or fluid motor for linearly advancing and retracting the control wire in relation to the device. In operation, when one of the control wires is pulled proximally by rotation of the drum or spool, the distal tip of the device bends at the steerable region toward the retracted wire.
As an aid to the early detection of disease, it has become well established that there are major public health benefits from regular endoscopic examinations of internal structures such as alimentary canals and airways, e.g., the esophagus, lungs, colon, uterus, and other organs. A conventional imaging endoscope used for such procedures comprises a flexible tube with a fiber optic light guide that directs illuminating light from an external light source to the distal tip where it exits the endoscope and illuminates the tissue to be examined. Frequently, additional optical components are incorporated to adjust the spread of light exiting the fiber bundle and the distal tip. An objective lens and fiber optic imaging light guide communicating with a camera at the proximal end of the scope, or an imaging camera chip at the distal tip, produce an image that is displayed to the examiner. In addition, most endoscopes include one or more working channels through which medical devices such as biopsy forceps, snares, fulguration probes, and other tools may be passed.
U.S. Pat. No. 5,679,216 describes a multi-degree-of-freedom manipulator including a flexible tube having a plurality of flex portions, a plurality of actuators made of shape memory alloy for flexing the flex portions, two common energy transmission paths for transmitting energy to the actuators, and selective energy supply members for controlling the energy supplied from the common energy transmission path to the actuators, thereby respectively independently driving the actuators to bend the flexible tube.
U.S. Pat. No. 4,432,349 describes an articulated tube structure for use in an endoscope or the like which consists of a number of elementary tubes connected in end-to-end relationship. Between the adjacent elementary tubes are provided springs to urge the articulated tube to bend in one direction. The articulated tube is spring urged in one direction and is manipulated to bend as desired by operation of pull wires extending through the articulated tube and fixed at their end to the head of the endoscope.
Navigating channels in the human body can be very challenging. Some parts of the human anatomy can be difficult to see and are not always oriented in a convenient location relative to the position of the scope or surgical instrument. Occasionally, the anatomy and the degrees of freedom of the instruments can impede or prevent successful navigation. During conventional colonoscopy procedures, a colonoscope is advanced through the tortuous sigmoid colon until the colonoscope reaches the descending colon. The colonoscope is then manipulated to reduce the redundancy in the sigmoid colon. When the sigmoid colon has been straightened, the colonoscope is typically further advanced through the colon. However, this type of procedure is generally difficult to perform, and/or painful for the patient due to stretching of the colon which occurs upon impact between the colonoscope and the wall of the colon as the colonoscope is advanced, especially during advancement of the colonoscope around the bends of the tortuous sigmoid colon. Navigation of the endoscope through complex and tortuous paths is critical to success of the examination with minimum pain, side effects, risk, or sedation to the patient. To this end, modern endoscopes include means for deflecting the distal tip of the scope to follow the pathway of the structure under examination, with minimum deflection or friction force upon the surrounding tissue. Control cables similar to puppet strings are carried within the endoscope body in order to connect a flexible portion of the distal end to a set of control knobs at the proximal endoscope handle. By manipulating the control knobs, the examiner is usually able to steer the endoscope during insertion and direct it to a region of interest, in spite of the limitations of such traditional control systems, which are clumsy, non-intuitive, and friction-limited. Common operator complaints about traditional endoscopes include their limited flexibility, limited column strength, and limited operator control of stiffness along the scope length.
Conventional endoscopes are generally built of sturdy materials, which decrease the flexibility of the scope and thus can decrease patient comfort. Furthermore, conventional endoscopes are complex and fragile instruments that frequently need costly repair as a result of damage during use or during a disinfection procedure. Still, many procedures using steerable instruments remain difficult. A great deal of skill and patience is often required to correctly orient the instrument in a predetermined position.